I installed 12.1 on my MacBook Pro 2.2, OS X 10.5.2 with no issues whatsoever. I quit all running processes first, repaired permissions afterwards with Onyx automation, then restarted, and v12.1 is running flawlessly. I have noticed a small speed increase in the scrolling of long docs as well. (Word).

Ancient Boii dude: I understand that you don't like the product. You don't have to, but posting 3 or 4 flame type comments with a 1 star rating on each of them is not what these forums are for, and it's dishonest. I also don't believe you. You've been around these forums long enough to know how to install a MS product, i.e. quitting background apps, and repairing permissions afterward. I've heard you be quite humorous and helpful in the past. Not today. Your posts here are tiresome, bitter and mean-spirited. You're slipping Ancient Boy.